Vehicle systems may include a plurality of vehicles that are connected to one another through couplers. The vehicles of a train, for instance, often include multiple locomotives (e.g., two, three, four, or more locomotives) and numerous rail vehicles (e.g., tens or hundreds of rail vehicles). The locomotives may have separate positions along a length of the train. For example, a first locomotive may be the leading vehicle of the train, a second locomotive may be positioned at about one-third of the length of the train, and a third locomotive may be positioned at about two-thirds of the length of the train. The locomotives collectively drive the train along a designated route. The length of the train may be a mile or greater, and the terrain along the route is often uneven with numerous turns. As such, separate vehicles of the train may experience different forces. For example, one locomotive may be moving along an incline while another locomotive is moving along a decline and/or a turn.
Each vehicle is coupled to one or two adjacent vehicles through the couplers. A coupler may include, among other things, one or more springs, dampers, and/or friction blocks. While the train moves along the track as described above, the couplers exhibit dynamic forces (e.g., compression, expansion, or zero force in a dead zone). The compression or expansion forces can damage the couplers when they exceed designated values. These forces can also cause fatigue during the lifetime operation of the coupler that renders the coupler more susceptible to damage. When a coupler is damaged, it may be necessary to stop the train and allow an individual to replace the damaged coupler. Accordingly, reducing the likelihood of damage to couplers may, among other things, decrease overall operational costs, decrease downtime, and increase network reliance on the schedule of a train.
Known vehicle systems may operate according to a trip plan that specifies how the vehicle system should operate to meet or achieve certain objectives during the trip. For example, the trip plan may specify throttle settings or brake settings of the vehicle system as a function of time, location, and/or other parameters. The trip plan may be created to, among other things, reduce the likelihood that the couplers are damaged. Constraints in creating the trip plan may include estimated arrival times, speed limits, emission limits, slow orders, and the like. Other information may be used to generate the trip plan, such as the length and weight of the vehicles, the grade and conditions of the route that the vehicle will be traversing, weather conditions, performance of the vehicle, slow orders for certain segments of the route, and/or the like.
Train handling can be a difficult problem to address while simultaneously attempting to achieve the other objectives in the trip plan (e.g., fuel efficiency, arrival time). For instance, the control system of the train (or the driver of the train) may be able to control only a few parameters, such as a notch setting or air brakes, as the train moves along the route. The train, however, may have hundreds of vehicles and, consequently, hundreds of couplers that connect the vehicles. As the train moves along a route, the individual vehicles may have different speeds and/or accelerations with respect to one another. If two adjacent vehicles have substantially different speeds, the compression or expansion forces between the two vehicles may damage the connecting coupler.
Presently, the control system may monitor a speed of the lead locomotive and compare that value to a value of the trip plan. For example, the measured value may be the actual speed of the lead locomotive and the planned value may be the center-of-mass (CM) speed of the train. If the values differ, the control system adjusts the operational settings of the train. As an example, if the speed of the lead locomotive at the notch setting of the trip plan exceeds the CM speed of the trip plan, the control system may automatically lower the notch setting or settings and/or activate the braking system. Although the above process may be effective in many situations, the couplers are still at risk of being damaged, especially along routes with an uneven terrain. Moreover, the lead speed, which represents the speed of a single vehicle, varies more than the CM speed, which is a function of the speeds of all the system vehicles. As such, the control system may frequently change the operational settings when such changes may be unnecessary.
It may also be desirable to monitor the performance of the vehicle system to determine whether the performance sufficiently matches the performance dictated by the trip plan. For example, the trip plan is often constructed based on a center-of-mass speed of the vehicle system. If the center-of-mass speed of the vehicle system as it travels along the route does not sufficiently match the center-of-mass speed dictated by the trip plan, adjustments to the operational settings can be made.
Accordingly, a need exists for alternative systems and methods for controlling operation of a vehicle system along a route to reduce the likelihood of damage to couplers of the vehicle system and/or to increase the likelihood that the performance of the vehicle system sufficiently matches the performance dictated by the trip plan.